Comet C/2014 Q2 Lovejoy on May 7 with its emerald coma and faint gas tail. Lovejoy is currently around magnitude +7.5 and slowly fading. Credit: Rolando Ligustri
Lots of towns hold a polar plunge fundraising event in the winter. Duluth, Minnesota’s version, where participants jump in Lake Superior every February, might just be the coldest. Comet Lovejoy’s a season behind, but sure enough, it’s following suit, diving deep into the dark waters of the north celestial pole this month.
I dropped in on our old friend last night, when it glowed only 8° from the North Star. In 8×40 binoculars, the comet was faintly visible as a hazy blob of light with a brighter center. Not a sight to knock you over, but the fact that this comet is still visible in binoculars after so many months makes it worthwhile to seek out. Moonless skies for the next 10-11 nights means lots of opportunities.
Just face the North Star (Polaris) to begin tracking Comet Lovejoy. The map shows the sky facing north around 10:30 p.m. local time in mid-May. Stars are plotted to magnitude +8. Click for a larger version. Source: Chris Marriott’s SkyMap
Unless a new comet is discovered, Lovejoy will continue to remain the only “bright” comet visible from mid-northern latitudes for some time. There’s a tiny chance Comet C/2014 Q1 PanSTARRS will wax bright enough to see in twilight in early July, but it will be very low in the northwestern sky at dusk and visible for a few nights at most. Only C/2013 US10 Catalina offers the chance for a naked eye / binocular appearance, when it re-emerges from the solar glare in the latter half of November in the morning sky.
Southern hemisphere observers have more to smile about with Comet C/2015 G2 MASTERcurrently flaunting its fluff at magnitude +6.6 or just under the naked eye limit. They’ll also get a far better view of C/2014 Q1 PanSTARRS come this July and August.
Wide view of the sky facing north in mid-May around 10:30 p.m. local time. Use the Pointer stars in the Big Dipper to point you to Polaris and from there to the comet. Source: Chris Marriott’s SkyMap
Through a telescope, Lovejoy still shows off a round, 6 arc minute diameter coma (one-fifth as wide as a full moon) and a denser, brighter core highlighted by a starlike false nucleus. We call it false because the true comet nucleus, probably no more than a few kilometers across, hides within a dusty cocoon of its own making. Only spacecraft have been able to get close enough for a clear view of comet nuclei. Each shows a unique and usually non-spherical shape because comets aren’t massive enough for their own self-gravity to crush them into spheres the way larger moons and planets do. If you’re a single object and big, being spherical comes naturally.
Comet Lovejoy will be closest to the imaginary point in the sky called the north celestial pole on May 29. Polaris lies 0.75° from the pole and describes a small circle 1.5° in diameter around it each day. Source: Stellarium
In my 15-inch (37-cm) telescope a faint wisp of a tail poked from the coma to the north. Looking at the map, you can see the comet’s headed due north through Cepheus toward Polaris, the North Star. Each passing night, it draws closer to the sky’s celestial pivot point, missing it by just 1° on the evenings of May 27 and 28. Closest approach to the north celestial pole, which marks the spot in the sky toward which Earth’s north polar axis currently points, occurs on May 29 with a separation of 54 arc minutes or just under a degree.
Finding Polaris is easy. Just draw a line through the two stars at the end of of the Big Dipper’s Bowl toward the horizon. The first similarly bright star you run into is the North Star. Using the map, you can navigate from Polaris to the fuzzy comet with either binoculars or telescope.
Comet G2 MASTER passes near the Helix Nebula in Aquarius on the night of April 21st.
Did you catch the performance of Comet C/2014 Q2 Lovejoy earlier this year? Every year provides a few sure bets and surprises when it comes to binocular comets, and while we may still be long overdue for the next truly ‘Great Comet,’ 2015 has been no exception.
This week, we’d like to turn your attention to two icy visitors to the inner solar system which may present the best bets comet-wise over the next few weeks: Comets C/2014 Q1 PanSTARRS and C/2015 G2 MASTER.
First up is Comet C/2014 Q1 PanSTARRS. Discovered on August 16, 2014 by the Panoramic Survey Telescope & Rapid Response System (PanSTARRS) based atop Mount Haleakala in Hawaii, we’ve known of the potential for Q1 PanSTARRS to put on a decent show this summer for a while. In fact, it made our roundup of comets to watch for in our 101 Astronomical Events for 2015. Q1 PanSTARRS currently sits at +11th magnitude as a morning sky object in the constellation Pisces. On a 39,000 year long parabolic orbit inclined 45 degrees relative to the Earth’s orbit, Q1 PanSTARRS will leap up across the ecliptic on May 17th and perhaps reach +3rd magnitude as it nears perihelion in early July and transitions to the evening sky.
An image of Comet C/2014 Q1 PanSTARRS shortly after discovery. Credit and copyright: Efrain Morales Rivera.
Though it may put on its best show in July and August, a few caveats are in order. First, we’ll be looking at Q1 PanSTARRS beyond the summer Sun, and like C/2011 L4 PanSTARRS a few years back, it’ll never leave the dusk twilight, and will always appear against a low contrast backdrop.
The May-June path of Comet Q1 PanSTARRS through the dawn sky as seen from latitude 30 degrees north. Credit: Starry Night Education software.
Here are some notable upcoming events for Comet C/2014 Q1 PanSTARRS:
(Unless otherwise noted, a ‘close pass’ is here considered to be less than one degree of arc, about twice the diameter of a Full Moon.)
May 16: Passes into the constellation Aries.
May 16: The waning crescent Moon passes 2 degrees distant.
May 17: Crosses northward through the ecliptic.
May 20: May break +10th magnitude.
June 11: Passes in to the constellation Taurus.
June 12: Passes 2 degrees from M45 (The Pleiades).
June 15: May break 6th magnitude.
June 20: Passes into Perseus.
June 21: Passes into Auriga.
June 23: Passes +2.7 magnitude star Hassaleh (Iota Aurigae).
June 25: Passes the +7.5 magnitude open cluster IC 410.
June 26: Passes +6 magnitude Pinwheel Open Cluster (M36).
The July-August evening path of Q1 PanSTARRS as seen from latitude 30 degrees north. Credit: Starry Night Education software.
July 2: Crosses into Gemini.
July 3: Passes the +3.6 magnitude star Theta Geminorum.
July 5: Passes 10 degrees north of the Sun and into the evening sky.
July 6: Passes midway between Castor and Pollux.
July 6: Reaches perihelion at 0.315 astronomical units (AU) from the Sun.
July 7: May top out at +3rd magnitude.
July 8: Crosses into Cancer.
July 12: Photo Op: passes M44, the Beehive Cluster.
July 13: Sits 30 degrees from Comet C/2015 G2 MASTER (see below).
July 15: May drop below +6th magnitude.
July 15: Crosses the ecliptic southward.
July 17: The waxing crescent Moon passes 1.5 degrees south.
July 19: Crosses into Leo.
July 20: Closest to Earth, at 1.18 AU distant.
July 21: Less than 10 degrees from Jupiter and Venus.
July 22: Crosses into Sextans.
July 26: Crosses the celestial equator southward.
August 4: Crosses into Hydra.
August 5: Crosses into Crater.
August 18: Crosses back into Hydra.
August 30: Crosses into Centaurus.
September 1: Drops below +10th magnitude.
The projected light curve of Q1 PanSTARRS over time. The black dots represent observations. Credit: Weekly Information about Bright Comets.
The next comet on deck is the recently discovered C/2015 G2 MASTER. If you live in the southern hemisphere, G2 MASTER is the comet that perhaps you haven’t heard of, but should be watching in the dawn sky. Discovered last month on April 7 as by MASTER-SAAO (The Russian built Mobile Astronomical System of Telescope-Robots at the South African Astronomical Observatory), this is not only the first comet bagged by MASTER, but the first comet discovery from South Africa since 1978. G2 MASTER has already reached magnitude +7 and is currently crossing the constellation Sculptor. It is also currently only visible in the dawn sky south of 15 degrees north latitude, but images already show a short spiky tail jutting out from G2 MASTER, and the comet may rival Q2 Lovejoy’s performance from earlier this year. Expect G2 MASTER to top out at magnitude +6 as it nears perihelion in mid-May. Observers around 30 degrees north latitude in the southern U.S. should get their first good looks at G2 MASTER in late May, as it vaults up past Sirius and breaks 10 degrees elevation in the evening sky after sunset. Again, as with Q1 PanSTARRS, cometary performance versus twilight will be key!
An April 10th image of Comet C/2015 G2 MASTER, plus an initial projected light curve versus solar elongation over time. Credit: Ernesto Guido & Nick Howes/Remanzacco Observatory
Here are some key dates with astronomical destiny for Comet G2 MASTER over the coming weeks:
May 9: Crosses into Fornax.
May 15: May top out at +6th magnitude.
May 13: Closest to Earth at 0.47 AU.
May 14: Crosses into Eridanus.
May 16: Crosses into Caelum.
May 17: Crosses into Lepus.
May 20: Passes the +3.8 magnitude star Delta Leporis.
May 23: Crosses into Canis Major.
May 23: Reaches perihelion at 0.8 AU from the Sun.
May 27: Crosses into Monoceros.
May 28: Passes the +5.9 magnitude Open Cluster M50.
Comet G2 MASTER imaged on May 7th. Credit and copyright: Adriano Valvasori
June 8: Crosses northward over the celestial equator and into the constellation Canis Minor.
July 1: May drop below 10th magnitude.
G2 MASTER also crosses SOHO’s field of view on July 24th through August 4th, though it may be too faint to see at this point.
Here are the Moon phases for the coming weeks to aid you in your comet quest:
Full Moons: June 2nd, July 2nd, July 31st, August 29th.
New Moons: May 18th, June 16th, July 16th, August 14th.
Binoculars are our favorite ‘weapon of choice’ for comet hunting. Online, Heavens-Above is a great resource for quickly and simply generating a given comet’s sky position in right ascension and declination; we always check out the Comet Observers Database and Seiichi Yoshida’s Weekly Information about Bright Comets to see what these denizens of the outer solar system are currently up to.
Good luck, and be sure to regale us with your comet-hunting tales of tragedy and triumph!
A lucky capture of a 2013 Lyrid meteor. Image credit and copyright: John Chumack
April showers bring May flowers, and this month also brings a shower of the celestial variety, as the Lyrid meteors peak this week.
And the good news is, 2015 should be a favorable year for the first major meteor shower of the Spring season for the northern hemisphere. The peak for the shower in 2015 is predicted to arrive just after midnight Universal Time on Thursday April 23rd, which is 8:00 PM EDT on the evening of Wednesday April 22nd. This favors European longitudes right around the key time, though North America could be in for a decent show as well. Remember, meteor showers don’t read forecasts, and the actual peak can always arrive early or late. We plan to start watching tonight and into Wednesday and Thursday morning as well. April also sees a extremely variable level of cloud cover over the northern hemisphere, another reason to start your meteor vigil early on if skies are clear.
The radiant for the 2015 Lyrids as seen from 40 degrees north latitude at local midnight. Credit: Stellarium.
Another favorable factor this year is the phase of the Moon, which is only a slender 20% illuminated waxing crescent on Wednesday night. This means that it will have set well before local midnight when the action begins.
The source of the Lyrid meteors is Comet C/1861 G1 Thatcher, which is on a 415 year orbit and is expected to come back around again in 2276 A.D. 1861 actually sported two great comets, the other being C/1861 J1, also known as the Great Comet of 1861.
The orientation of the Sun, Moon, and the Lyrid radiant at the expected peak of the shower at 24UT/20EDT April 22nd. credit: Stellarium
The Lyrids typically exhibit an ideal Zenithal Hourly Rate (ZHR) of 15-20 per hour, though this shower has been known to produce moderate outbursts from time to time. In 1803 and 1922, the Lyrids produced a ZHR of 100 per hour, and in recent times, we had an outburst of 250 per hour back in 1982. Researchers have tried over the years to tease out a periodicity for Lyrid outbursts, which seem erratic at best. In recent years, the Lyrids hit a ZHR of 20 (2011), 25 (2012), 22 (2013), and 16 last year in 2014.
Keep in mind, we say that the ZHR is an ideal rate, or what you could expect from the meteor shower with the radiant directly overhead under dark skies: expect the actual number of meteors observed during any shower to be significantly less.
A 2014 Lyrid fireball. Credit: The UK Meteor Network
The radiant for the Lyrids actually sits a few degrees east of the bright star Vega across the Lyra border in the constellation Hercules. They should, in fact, be named the Herculids! In mid-April, the radiant for the April Lyrids has already risen well above the northeastern horizon as seen from latitude 40 degrees north at 10 PM local, and is roughly overhead by 4 AM local. Several other minor showers are also active around late April, including the Pi Puppids (April 24th), the Eta Aquarids (May 6th), and the Eta Lyrids (May 9th). The constellation of the Lyre also lends its name to the June Lyrids peaking around June 6th.
The April Lyrids are intersecting the Earth’s orbit at a high 80 degree angle at a swift velocity of 49 kilometres per second. About a quarter of the Lyrid meteors are fireballs, leaving bright, persistent smoke trains. It’s a good idea to keep a set of binoculars handy to study these lingering smoke trails post-passage.
The Lyrids also have the distinction of having the longest recorded history of any known meteor shower. Chinese chronicles indicate that “stars dropped down like rain,” on a late Spring night in 687 BC.
Observing a meteor shower requires nothing more than a set of working ‘Mark-1 eyeballs’ and patience. The International Meteor Organization always welcomes reports of meteor counts from observers worldwide to build an accurate picture of evolving meteor debris streams. You can even hear meteor ‘pings’ via FM radio.
Expect the rate to pick up past local midnight, as the Earth plows headlong into the oncoming meteor stream. Remember, the front of the car gets the love bugs, an apt analogy for any Florida resident in mid-April.
A composite view of the 2012 Lyrids plus sporadic meteors. Credit: NASA/MSFC/Danielle Moser
Catching a photograph of a Lyrid or any meteor is as simple as plopping a DSLR down on a tripod and doing a series of 30 second to several minute long time exposures. Use the widest field of view possible, and aim the camera off at about a 45 degree angle from the radiant to catch the meteors sidelong in profile. Be sure to take a series of test shots to get the ISO/f-stop combination set for the local sky conditions.
Don’t miss the 2015 Lyrids, possibly the first good meteor shower of the year!
Calling all light-bucket scope owners: the folks at the European Space Agency want to enlist you in the quest to monitor Comet 67P/Churyumov-Gerasimenko from our Earthbound perspective through perihelion later this summer.
“We are looking to bring an entire community of professional and amateur observers together,” said Rosetta Coordinator of Amateur Observations for Comet 67/P C-G Padma A. Yanamandra-Fisher in a recent press release. “When else can you observe a comet at the same time a spacecraft is viewing it at close proximity and escorting it to perihelion, and be able to correlate both sets of findings?
The Rosetta story thus far has been an amazing tale of discovery. We’ve extensively chronicled the historic approach of the Rosetta spacecraft as the rubber-duck-shaped comet grew in its view here at Universe Today. The world also held its collective breath as the Philae lander, the little washing Euro- washing machine-sized spacecraft that could, descended on to the alien surface. Heck, Philae even knocked a Kardashian out of the top trending spot worldwide, a feat in and of itself.
Prospects in 2015: As of this writing, Comet 67P/C-G is 1.9 AU from the Sun and closing. The ‘P’ in ‘67/P’ stands for ‘short term (less than 200 years) periodic,’ and the comet orbits the Sun once every 6.44 years. Perihelion for 67/P occurs on August 13th, 2015 when the comet reaches a distance of 1.24 AU ( 191 million kilometres) from the Sun.
Discovered in 1969 by the Kiev University’s Klim Ivanovych Churyumov while examining a photograph taken by Svetlana Gerasimenko, this is the comet’s seventh apparition. Currently shining at +18th magnitude in the constellation Aquarius, Comet 67P C-G will vault up in the early morning sky for northern hemisphere observers and cross the ecliptic plane in the last week of July, at 43 degrees elongation west of the Sun.
The comet is expected to reach a maximum brightness of +11th magnitude near perihelion. Historically, 67P – like most comets – tend to under-perform before perihelion, only to have an energetic lingering outburst phase post-perihelion.
“With each apparition we see it (67P) behave differently.” Yanamandra-Fisher said. “These legacy data sets will aid in our knowledge of this comet, especially when used in combination with the data gathered by the Rosetta spacecraft and the new ground observations made this year.”
The path of 67/P through the morning sky as seen from latitude 30 degrees north. Image credit: Starry Night Education software
Time on professional scopes is always chronically in short supply, with more astronomers and targets to observe than there are telescopes available. That’s where amateur observers come in. Many private backyard observatories have instruments that would be the envy of many a major institution. Though the press release suggests that the minimum aperture size needed to observe 67P this summer is 14-inches (35 cm), we urge 10” or 12” inch scope owners – especially those who have the latest generation of Mallincam and faint object CCD imagers – to give it a try. We’ve seen some amazing results with these, even during quick casual observing sessions such as public star parties! The Rosetta team is looking for everything from professional grade images, to sketches and visual observations with magnitude estimations.
Of course, hunting faint comets is a daunting task at best. +10th magnitude is generally our cut-off for ‘is interesting enough to alert the public’ in terms of novae or comets, though we’ll let 67/P ‘into the club’ due to its celebrity status.
To add to the challenge, the comet is only visible against a dark sky during a brief pre-dawn window. You’ll need a planetarium program (we use Starry Night Pro) to generate good finder charts down to 15th magnitude or so. Keep in mind, comets also typically appear a bit fainter visually than stars of the same magnitude due to the fact that said brightness is spread out over a broad surface area.
“This is truly interactive science that people of all observing levels can participate in- from amateurs to professionals.” Yanamandra-Fischer said in closing.
Other comets to watch for in 2015 include still bright 2014 Q2 Lovejoy, C/2013 US10 Catalina, C/2014 Q1 PanSTARRS, and 19P/Borrelly.
What’ll happen as 67P approaches perihelion? Will those two gigantic lobes crack and separate as Rosetta and the world looks on? Now, I’d pay to see that!
A light bucket scope at the Bruneau Dunes observatory suitable for a faint comet quest. Image credit: David Dickinson
Artist rendition of the Philae lander on Comet 67P/Churyumov-Gerasimenko. Credit: DLR.
Where is the Philae lander and will it wake up again? Those are the questions the team at the DLR Lander Control Center will be trying to answer starting this week. Thursday, March 12 provides the first possibility to receive a signal from Rosetta’s lander, sitting somewhere on Comet 67P/Churyumov-Gerasimenko.
“It could be that the lander has already woken up from its winter sleep 500 million kilometers away, but does not yet have sufficient power to inform the team on Earth,” said Koen Geurts from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt) in a blog post today.
The animated image below provides strong evidence that Philae touched down for the first time almost precisely where intended. The animation comprises images recorded by Rosetta’s navigation camera as the orbiter flew over the (intended) Philae landing site on November 12th. The dark area is probably dust raised by the craft on touchdown. The boulder to the right of the circle is seen in detail in the photo below. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
The lander has been sleeping in a shaded spot on the comet’s surface after its dramatic touchdown (actually, three touchdowns) four months ago on Nov. 12, 2014 when it flew, landed, bounced and then repeated that process for more than two hours across the surface. Scientists estimated it could have bounced as high as 3.2 kilometers (2 miles) before becoming wedged in a spot that –- at that time — didn’t get much sunlight. The solar-powered lander quickly ran out of power, just hours after landing.
The team admits they would be very lucky if a signal were to be received from Philae at the first opportunity, which is 05:00 CET on March 12, 2015 (midnight on March 11 EDT) when the communication unit on the Rosetta orbiter will be switched on to call the lander.
While the comet is coming ever-closer to the Sun, Philae needs to receive enough solar energy to activate a few systems before it can wake up and begin communicating.
“Philae currently receives about twice as much solar energy as it did in November last year,” said Lander Project Manager Stephan Ulamec from DLR. “Comet 67P/Churyumov-Gerasimenko and its companion, Philae, are now only 300 million kilometers from the Sun. It will probably still be too cold for the lander to wake up, but it is worth trying. The prospects will improve with each passing day.”
The team did give a caveat that several conditions must be met for Philae to wake up and start operating again. By no means is it a given that Philae will awake.
First, the interior of the lander must be at least at minus 45 degrees Celsius before Philae can wake up from its winter sleep. In addition, the lander must be able to generate at least 5.5 watts using its solar panels to wake up. The temperatures are significantly lower in the shadowed region where it sits (named Abydos, even though the exact location has not been identified) than at the originally planned landing location.
While hibernating, the lander has been gathering and storing as much power as possible to heat up and Geurts said that as soon as Philae ‘realizes’ that it is receiving more than 5.5 watts of power and its internal temperature is above minus 45 degrees Celsius, it will turn on, heat up further and attempt to charge its battery.
Then, once awakened, Philae will switch on its receiver every 30 minutes and listens for a signal from the Rosetta orbiter. This, too, can be performed in a very low power state, but Philae needs a total of 19 watts to begin operating and allow two-way communication.
Until March 20, Rosetta will be transmitting to the lander and listening for a response. The team said the most likely time for contact is during the 11 flybys where the orbiter’s path puts it in a particularly favorable position with respect to the lander during comet ‘daytime’ – that is, when Philae is in sunlight and being supplied with power by its solar panels. Communication will be attempted continuously because Philae’s environment could have changed since the landing.
“If we cannot establish contact with Philae before 20 March, we will make another attempt at the next opportunity,” said Ulamec. “Once we can communicate with Philae again, the scientific work can begin.”
Once Philae wakes up and can transmit, it will first send data about the health of its systems.
“We will then evaluate the data. What is the state of the rechargeable battery? Is everything on the lander still functioning? What is the temperature? How much energy is it receiving?” said Geurts.
Then the team will determine if all 10 instruments will be able to function with the available power. If sufficient energy cannot be stored in the battery, the solar energy available during the comet daytime will determine whether a reduced version of the science operations can be performed.
Currently, scientists believe that Philae is in sunlight for 1.3 hours. A day on 67P/Churyumov-Gerasimenko lasts 12.4 hours. If the battery can be charged as planned, then science operations could be done even at night. But in the event that the rechargeable battery on board Philae did not survive the intense cold of its hibernation, the engineers are prepared. “We are working to ensure that we can operate the lander and its instruments at least during the comet’s daytime, when it is in direct sunlight.”
Also, new commands have been sent to Philae to optimize the heating and provide energy savings to improve its chances of communication with Earth. Even if Philae does not have enough energy yet to answer, it could receive and execute these commands. This is referred to as ‘blind commanding’ by the engineers, because the lander is initially very unlikely give them feedback.
Philae’s exact location is still being determined by looking at images acquired by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) on board the Rosetta orbiter.
Montage of four single-frame images of Comet 67P/C-G taken by Rosetta’s Navigation Camera (NAVCAM) at the end of February 2015. The images were taken on 25 February (top left), 26 February (top right) and on two occasions on 27 February (bottom left and right). Exposure times are 2 seconds each and the images have been processed to bring out the details of the comet's many jets. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
Tell me this montage shouldn’t be hanging in the Lourve Museum. Every time I think I’ve seen the “best image” of Rosetta’s comet, another one takes its place. Or in this case four! When you and I look at a comet in our telescopes or binoculars, we’re seeing mostly the coma, the bright, fluffy head of the comet composed of dust and gas ejected by the tiny, completely invisible, icy nucleus.
As we examine this beautiful set of photos, we’re privileged to see the individual fountains of gas and dust that leave the comet to create the coma. Much of the outgassing comes from the narrow neck region between the two lobes.
This photo taken on Feb. 27 shows the comet with peacock-like display of dusty jets. Below center is a streak that may be a dust particle that traveled during the exposure. Other small white spots are also likely dust or bits of comet that have broken off. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
All were taken between February 25-27 at distances around 50-62 miles (80 to 100 km) from the center of Comet 67P/Churyumov-Gerasimenko. Looking more closely, the comet nucleus appears to be “glowing” with a thin layer of dust and gas suspended above the surface. In the lower left Feb. 27 image, a prominent streak is visible. While this might be a cosmic ray zap, its texture hints that it could also be a dust particle captured during the time exposure. Because it moved a significant distance across the frame, the possible comet chunk may be relatively close to the spacecraft. Just a hunch.
Another close-up individual image from Rosetta’s NAVCAM. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
While most of Rosetta’s NAVCAM images are taken for navigation purposes, these images were obtained to provide context in support of observations performed at the same time with the Alice ultraviolet (UV) imaging spectrograph on Rosetta. Observing in ultraviolet light, Alice determines the composition of material in coma, the nucleus and where they interface. Alice will also monitor the production rates of familiar molecules like H2O, CO (carbon monoxide) and CO2 as they leave the nucleus and enter 67P’s coma and tail.
Alice makes its observations in UV light through a long, narrow slit seen here superimposed on a graphic of comet 67P/ C-G. Credit: ESA/NASA
From data collected so far, the Alice team has discovered that the comet is unusually dark in the ultraviolet, and that its surface shows no large water-ice patches. Water however has been detected as vapor leaving the comet as it’s warmed by the Sun. The amount varies as the nucleus rotates, but the last published measurements put the average loss rate at 1 liter (34 ounces) per second with a maximum of 5 liters per second. Vapors from sublimating carbon monoxide and carbon dioxide ice have also been detected. Sometimes one or another will dominate over water, but overall, water remains the key volatile material outgassed in the greatest quantity.
Particularly striking and collimated jets emerge from the comet’s shadowed Hathor region between the two lobes. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0Look at those spirals! In this separate image, taken Feb. 28, ESA suggests the curved shape of the outflowing material likely results from a combination of several factors, including the rotation of the comet, differential flows of near-surface gas, and gravitational effects arising due to the uneven shape of the comet. The viewing perspective of the image might also distort the true shape of the outflowing material. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
That and dust. In fact, 67P is giving off about twice as much dust as gas. We see the comet’s dual emissions by reflected sunlight, but because there’s so much less material in the jets than what makes up the nucleus, they’re fainter and require longer exposures and special processing to bring out without seriously overexposing the comet’s core.
67P’s coma will only grow thicker and more intense as it approaches perihelion on August 13.
Headless comet D1 SOHO photographed in evening twilight on Feb. 28. Credit: Michael Jaeger
Like coins, most comet have both heads and tails. Occasionally, during a close passage of the Sun, a comet’s head will be greatly diminished yet still retain a classic cometary outline. Rarely are we left with nothing but a tail. How eerie it looks. Like a feather plucked from some cosmic deity floating down from the sky. Welcome to C/2015 D1 SOHO, the comet that almost didn’t make it.
It was discovered on Feb. 18 by Thai amateur astronomer and writer Worachate Boonplod from the comfort of his office while examining photographs taken with the coronagraph on the orbiting Solar and Heliospheric Observatory (SOHO). A coronagraph blocks the fantastically bright Sun with an opaque disk, allowing researchers to study the solar corona as well as the space near the Sun. Boonplod regularly examines real-time SOHO images for comets and has a knack for spotting them; in 2014 alone he discovered or co-discovered 35 comets without so much as putting on a coat.
Learn why there are so many sungrazing comets
Most of them belong to a group called Kreutz sungrazers, the remains of a much larger comet that broke to pieces in the distant past. The vast majority of the sungrazers fritter away to nothing as they’re pounded by the Sun’s gravity and vaporize in its heat. D1 SOHO turned out to be something different – a non-group comet belonging to neither the Kreutz family nor any other known family.
After a perilously close journey only 2.6 million miles from the Sun’s 10,000° surface, D1 SOHO somehow emerged with two thumbs up en route to the evening sky. After an orbit was determined, we published a sky map here at Universe Today encouraging observers to see if and when the comet might first become visible. Although it was last seen at around magnitude +4.5 on Feb. 21 by SOHO, hopes were high the comet might remain bright enough to see with amateur telescopes.
On Wednesday evening Feb. 25, Justin Cowart, a geologist and amateur astronomer from Alto Pass, Illinois figured he’d have a crack at it. Cowart didn’t have much hope after hearing the news that the comet may very well have crumbled apart after the manner of that most famous of disintegrators, Comet ISON . ISON fragmented even before perihelion in late 2013, leaving behind an expanding cloud of exceedingly faint dust.
Animation showing the D1 SOHO comet and its position marked on an atlas based on its orbit. Credit: Justin Cowart / José Chambo
Cowart set up a camera and tracking mount anyway and waited for clearing in the west after sunset. Comet D1 SOHO was located some 10° above the horizon near the star Theta Piscium in a bright sky. Justin aimed and shot:
“I was able to see stars down to about 6th magnitude in the raw frames, but no comet,” wrote Cowart. “I decided to stack my frames and see if I could do some heavy processing to bring out a faint fuzzy. To my surprise, when DeepSkyStacker spit out the final image I could see a faint cloud near Theta Picsium, right about where the comet expected to be!”
Cowart sent the picture off to astronomer Karl Battams, who maintains the Sungrazer Project website, for his opinion. Battams was optimistic but felt additional confirmation was necessary. Meanwhile, comet observer José Chambogot involved in the discussion and plotted D1’s position on a star atlas (in the blinking photo above) based on a recent orbit calculation. Bingo! The fuzzy streak in Justin’s photo matched the predicted position, making it the first ground-based observation of the new visitor.
Comet D1 SOHO’s orbit is steeply inclined to the ecliptic. It’s now headed into the northern sky, sliding up the eastern side of Pegasus into Andromeda as it recedes from both Earth and Sun. Credit: JPL Horizons
Comet D1 SOHO’s orbit is steeply inclined (70°) to the Earth’s orbit. After rounding the Sun, it turned sharply north and now rises higher in the western sky with each passing night for northern hemisphere skywatchers. Pity that the Moon has been a harsh mistress, washing out the sky just as the comet is beginning to gain altitude. These less-than-ideal circumstances haven’t prevented other astrophotographers from capturing the rare sight of a tailless comet. On Feb. 2, Jost Jahn of Amrum, Germany took an even clearer image, confirming Cowart’s results.
This photo, which confirmed Justin Cowart’s observation, was taken on Feb. 27 from Germany. Jost Jahn stacked 59 15-second exposures (ISO 1600, f/2.4) taken with an 85mm telescope to capture D1’s faint tail. Credit: Jost Jahn
To date, there have been no visual observations of D1 SOHO made with binoculars or telescopes, so it’s difficult to say exactly how bright it is. Perhaps magnitude +10? Low altitude, twilight and moonlight as well as the comet’s diffuse appearance have conspired to make it a lofty challenge. That will change soon.
Comet D1 SOHO’s dim remnant on Feb. 28, 2015 looks like it was applied with spray paint. Credit: Francois Kugel / fkometes.pagesperso-orange.fr/index.html
Once the Moon begins its departure from the evening sky on March 6-7, a window of darkness will open. Fortuitously, D1 SOHO will be even higher up and set well after twilight ends. I’m as eager as many of you are to train my scope in its direction and bid both hello and farewell to a comet we’ll never see again.
Map to help you find Comet C/2015 D1 SOHO March 2-7 around 7 p.m. (CST) and 8 p.m. CDT on March 8. Stars are shown to magnitude 8. See also below. Source: Chris Marriott’s SkyMap
Here are fresh maps based on the most recent orbit published by the Minor Planet Center. Assuming you wait until after Full Moon, start looking for the comet in big binoculars or a moderate to large telescope right at the end of evening twilight when it’s highest in a dark sky. The comet sets two hours after the end of twilight on March 7th from the central U.S.
Broader view with north up and west to the right showing nightly comet positions at 7 p.m. CST through March 7 and then 8 p.m. CDT thereafter. Stars to magnitude +9. Click to enlarge. Source: Chris Marriott’s Stellarium
Comet 2014 Q2 Lovejoy on December 27, 2014, as seen by the Dark Energy Survey. Credit: Fermilab’s Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny.
Oops! In a happy accident, Comet Lovejoy just happened to be in the field of view of the 570-megapixel Dark Energy Camera, the world’s most powerful digital camera. One member of the observing team said it was a “shock” to see Comet Lovejoy pop up on the display in the control room.
“It reminds us that before we can look out beyond our Galaxy to the far reaches of the Universe, we need to watch out for celestial objects that are much closer to home!” wrote the team on the Dark Energy Detectives blog.
On December 27, 2014, while the Dark Energy Survey was scanning the southern sky, C2014 Q2 entered the camera’s view. Each of the rectangular shapes above represents one of the 62 individual fields of the camera.
At the time this image was taken, the comet was passing about 82 million km (51 million miles) from Earth. That’s a short distance for the Dark Energy Camera, which is sensitive to light up to 8 billion light years away. The comet’s center is likely made of rock and ice and is roughly 5 km (3 miles) across. The visible coma of the comet is a cloud of gas and dust about 640,000 km (400,000 miles) in diameter.
The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision.
The camera just finished up the third, six-month-long season of observations, and the camera won’t be observing again until this fall.
You can download higher resolution versions of this image here.
Photo taken at 20:00 UT (2 pm. CST) Feb. 19 with the SOHO C2 coronagraph, a device that blocks the Sun, allowing a view of the area close by. Credit: NASA/ESA
A newly-discovered comet may soon become bright enough to see from a sky near you. Originally dubbed SOHO-2875, it was spotted in photos taken by the Solar and Heliospheric Observatory(SOHO) earlier this week. Astronomer Karl Battams, who maintains the Sungrazer Project website, originally thought this little comet would dissipate after its close brush with the Sun. To his surprise, it outperformed expectations and may survive long enough to see in the evening sky.
C/2015 D1 (SOHO) seen in a second, wide-field coronograph called LASCO C3 at 2:42 a.m. Feb. 20. Since then it’s well to the east of the Sun into the evening sky. Credit: NASA/ESA
Most sungrazing comets discovered by SOHO are members of the Kreutz family, a group of icy fragments left over from the breakup of a single much larger comet centuries ago. We know they’re all family by their similar orbits. The newcomer, SOHO’s 2,875th comet discovery, is a “non-group” comet or one that’s unrelated to the Kreutz family or any other comet club for that matter. According to Battams these mavericks appear several times a year. As of today (Feb. 24) its official name is C/2015 D1 (SOHO).
Composite of Comet SOHO-2875 crossing the C2 coronagraph field Feb. 19. Credit: NASA/ESA/Barbara Thompson
What’s unusual about #2,875 is how bright it is. At least for now, it appears to have survived the Sun’s heat and gravitational tides and is turning around to the east headed for the evening sky. Before it left SOHO’s field of view on Feb. 21, the comet was still around magnitude +4-4.5.
No one can say for sure whether it has what it takes to hang on, so don’t get your hopes up just yet. Battams and others carefully calculated the comet’s changing position in the SOHO images and sent the data off to the Minor Planet Center, which today published an orbit.
Newly-named Comet C/2015 D1 (SOHO) will share the sky with Venus and Mars at dusk. For the next few nights it will be quite low and nearly impossible to see. Its situation improves over time as the comet moves rapidly northward into Pegasus and Andromeda. Tick marks show the comet’s position each evening. Stars are shown to magnitude +6.5. Created with Chris Marriott’s SkyMap software
Based on this preliminary orbit, I’ve plotted SOHO-2875’s path for the next couple weeks as it tracks up through Pisces and Pegasus during the early evening hours. Given that it’s probably no brighter than magnitude +6 at the moment and very low in the west at dusk, it may still be swamped in twilight’s glow.
Barring an unexpected outburst, there’s no question that the comet will fade in the coming days as its distance from both the Earth and Sun increase. Right now it’s 79 million miles from us and 28 million miles from the Sun. That puts it about 8 million miles closer to the Sun than the planet Mercury.
Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA
I drew up the chart for about 75 minutes after sunset in late twilight. Keep in mind that since the comet’s positions were determined via spacecraft imagery, which isn’t as precise as photographing it from ground observatories, its orbit is preliminary. That means it may not be on the precise path shown on the map. Be sure you search up-down and right-left of the plotted locations.
It’s also very possible the comet is in the process of disintegration after perihelion passage, so it may not be a dense, compact object but rather a diffuse cloud of glowing dust. Will it go the way of Comet ISON and fade away to nothing? Who knows? I sure don’t but can’t wait to find out what it’s up to the next clear night.
BTW, if you’ve got a software program that downloads orbital elements for comets to create your own charts, you’ll find the numbers you need in today’s Minor Planet Circular. Be sure to use the “post-perihelion” elements that predict the comet’s location from here on out.
A binary star system Credit: Michael Osadciw/University of Rochester
Astronomers have reported the discovery of a star that passed within the outer reaches of our Solar System just 70,000 years ago, when early humans were beginning to take a foothold here on Earth. The stellar flyby was likely close enough to have influenced the orbits of comets in the outer Oort Cloud, but Neandertals and Cro Magnons – our early ancestors – were not in danger. But now astronomers are ready to look for more stars like this one.
A comparison of the Solar System and its Oort Cloud. 70,000 years ago, Scholz’s Star and companion passed along the outer boundaries of our Solar System (Credit: NASA, Michael Osadciw/University of Rochester, Illustration-T.Reyes)
Lead author Eric Mamajek from the University of Rochester and collaborators report in The Closest Known Flyby Of A Star To The Solar System (published in Astrophysical Journal on February 12, 2015) that “the flyby of this system likely caused negligible impact on the flux of long-period comets, the recent discovery of this binary highlights that dynamically important Oort Cloud perturbers may be lurking among nearby stars.”
The star, named Scholz’s star, was just 8/10ths of a light year at closest approach to the Sun. In comparison, the nearest known star to the Sun is Proxima Centauri at 4.2 light years.
While the internet has been rife with threads and accusations of a Nemesis star that is approaching the inner Solar System and is somehow being “hidden” by NASA, this small red dwarf star with a companion represents the real thing.
In 1984, the paleontologists David Raup and Jack Sepkoski postulated that a dim dwarf star, now widely known on the internet as the Nemesis Star, was in a very long period Solar orbit. The elliptical orbit brought the proposed star into the inner Solar System every 26 million years, causing a rain of comets and mass extinctions on that time period. By no coincidence, because of the sheer numbers of red dwarfs throughout the galaxy, Scholz’s star nearly fits such a scenario. Nemesis was proposed to be in a orbit extending 95,000 A.U. compared to Scholz’s nearest flyby distance of 50,000 A.U. Recent studies of impact rates on Earth, the Moon and Mars have discounted the existence of a Nemesis star (see New Impact Rate Count Lays Nemesis Theory to Rest, Universe Today, 8/1/2011)
But Scholz’s star — a real-life Oort Cloud perturber — was a small red dwarf star star with a M9 spectral classification. M-class stars are the most common star in our galaxy and likely the whole Universe, as 75% of all stars are of this type. Scholz’s is just 15% of the mass of our Sun. Furthermore, Scholz’s is a binary star system with the secondary being a brown dwarf of class T5. Brown Dwarfs are believed to be plentiful in the Universe but due to their very low intrinsic brightness, they are very difficult to discover … except, as in this case, as companions to brighter stars.
The astronomers reported that their survey of new astrometric data of nearby stars identified Scholz’s as an object of interest. The star’s transverse velocity was very low, that is, the stars sideways motion. Additionally, they recognized that its radial velocity – motion towards or away from us, was quite high. For Scholz’s, the star was speeding directly away from our Solar System. How close could Scholz’s star have been to our system in the past? They needed more accurate data.
The collaborators turned to two large telescopes in the southern hemisphere. Spectrographs were employed on the Southern African Large Telescope (SALT) in South Africa and the Magellan telescope at Las Campanas Observatory, Chile. With more accurate trangental and radial velocities, the researchers were able to calculate the trajectory, accounting for the Sun’s and Scholz’s motion around the Milky Way galaxy.
Scholz’s star is an active star and the researchers added that while it was nearby, it shined at a dimly of about 11th magnitude but eruptions and flares on its surface could have raised its brightness to visible levels and could have been seen as a “new” star by primitive humans of the time.
The relative sizes of the inner Solar System, Kuiper Belt and the Oort Cloud. (Credit: NASA, William Crochot)
At present, Scholz’s star is 20 light years away, one of the 70 closest stars to our Solar System. However, the astronomers calculated, with a 98% certainty, that Scholz’s passed within 0.5 light years, approximately 50,000 Astronomical Units (A.U.) of the Sun.
An A.U. is the mean distance from the Earth to the Sun and 50,000 is an important mile marker in our Solar System. It is the outer reaches of the Oort Cloud where billions of comets reside in cold storage, in orbits that take hundreds of thousands of years to circle the Sun.
With this first extraordinary close encounter discovered, the collaborators of this paper as well as other researchers are planning new searches for “Nemesis” type stars. The Large Synoptic Survey Telescope (LSST) and other telescopes within the next decade will bring an incredible array of data sets that will uncover many more red dwarf, brown dwarf and possibly orphan planets roaming in nearby space. Some of these could likewise be traced to past or future near misses to the Sun and Earth system.
