NASA's Perseverance Mars rover used its Mastcam-Z camera to capture the silhouette of Phobos, the larger of Mars' pair of moons, as it passed in front of the Sun on Feb. 8, 2024, the 1,056th Martian day, or sol, of the mission. Image Credit: NASA/JPL-Caltech/ASU/MSSS/SSI
NASA’s Perseverance rover is busy exploring the Martian surface and collecting samples for eventual return to Earth. But the rover recently took some time to gaze upward and observe the heavens. Using Mastcam-Z, the rover’s primary science camera, Perseverance captured Phobos, Deimos, and Mercury as they transited in front of the Sun.
This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image between the planet and Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Credit: ESO/M. Kornmesser
Our closest stellar neighbor is Proxima Centauri, an M-type (red dwarf) star located over 4.24 light-years away (part of the Alpha Centauri trinary system). In 2016, the astronomical community was astounded to learn that an Earth-like planet orbited within this star’s circumsolar habitable zone (HZ). In addition to being the closest exoplanet to Earth, Proxima b was also considered the most promising place to look for extraterrestrial life for a time.
Unfortunately, the scientific community has been divided on whether or not life could even be possible on this planet. All of these studies indicate that this question cannot be answered until astronomers characterize Proxima b’s atmosphere, ideally by observing it as it passes in front (aka. transited) of its host star. But in a new NASA-supported study, a team led by astrophysicists at the University of Chicago determined that this is an unlikely possibility.
TOI 1338 b is a circumbinary planet orbiting its two stars. It was discovered by TESS. Image Credit: NASA's Goddard Space Flight Center/Chris Smith
Researchers working with data from NASA’s TESS (Transiting Exoplanet Survey Satellite) have a found a planet that orbits two stars. Initially, the system was identified by citizen scientists as a pair of eclipsing binary stars without a planet. But an intern taking a closer look at that data found that it was misidentified.
Lasers like this one, at the VLT in Paranal, help counteract the blurring effect of the atmosphere. Powerful arrays of much larger lasers could hide our presence from aliens. (ESO/Y. Beletsky)
Of course we all know that aliens want to take over Earth. It’s in all the movies. And after they take over, they could do whatever they want to us puny, weak Earthlings. Enslavement? Yup. Forced breeding programs? Sure. Lay eggs in our bellies and consume our guts for their first meal? Why not.
But here at Universe Today, we’re science-minded types. We love the science fiction, but don’t take it too seriously. But someone we do take seriously when he has something to tell us is Stephen Hawking. And when he warned us that aliens might want to conquer and colonize us, it lent gravity to the whole discussion around contact with aliens. Should we reach out to alien civilizations? Will we be safe if they find us? Or should we try to conceal our presence?
If we choose concealment, then a new paper from two astronomers at New York’s Columbia University have good news for humanity. The authors of the paper, Professor David Kipping and graduate student Alex Teachey, say that lasers could be used to hide Earth from alien prying eyes.
At the heart of this whole idea are transits. When a planet passes in between its star and a distant observer, the star’s light is dimmed, and that’s called a transit. This is how the Kepler spacecraft detects exo-planets, and it’s been remarkably successful. If alien species are using the same method, which makes sense, then Earth would be easily detectable in the Sun’s habitable zone.
According to Kipping and Teachey, lasers could be used to mask this effect. A 30 MW laser would be enough to counter the dimming effect of Earth’s transit in front of the Sun. And it would only need to be turned on for 10 hours, once every year, since that’s how long Earth’s transit takes.
But that would only take care of the dimming effect in visible light. To counter-act the transit dimming across the whole electromagnetic spectrum would require much more energy: a 250 MW cloak of lasers tuned all across the spectrum. But there might be a middle way.
According to an interview with the paper’s authors in Science Daily, it might take only 160 MW of lasers to mask biological signatures in the atmosphere. Any prying alien eyes would not notice that life had ever come into being on Earth.
Should we decide that we do indeed want to be colonized, or forced to take part in breeding programs, or be enslaved, then the same system of lasers could be used to amplify the transit effect. This would make it easier, rather than harder, for aliens to detect us. In fact, according to the authors, these lasers could even be used to communicate with aliens, by transmitting information.
Of course, there’s one other element to all this. For this to work, we have to know where to aim the lasers, which means we have to know where the alien civilization is. And if we’re worried about them coming to get us, they will have more advanced technology than us. And if they have more advanced technology than us, they will for sure already have laser cloaking like the type talked about here.
So who’ll be the first to blink, and turn off their laser cloaking and allow detection?
An animated history of planetary detection, from 1750 to 2015. It shows the period (x-axis), mass (y-axis), radius (circle size) and detection method (color) of the 1800 plus planets now known. Credit and copyright: Hugh Osborn.
Early astronomers realized some of the “stars” in the sky were planets in our Solar System, and really, only then did we realize Earth is a planet too. Now, we’re finding planets around other stars, and thanks to the Kepler Space Telescope, we’re able to find planets that are even smaller than Earth.
This great new graphic of the history of planetary detection was put together by Hugh Osborn, a PhD student at the University of Warwick, who works with data from the WASP (Wide Angle Search for Planets) and NGTS (Next Generation Transit Survey) telescope surveys to discover exoplanets. It starts with the first real “discovery’ of a planet — Uranus in 1781 by William and Caroline Herschel.
“The idea of this plot is to compare our own Solar System (with planets plotted in dark blue) against the newly-discovered extrasolar worlds,” wrote Osborn on his website. “Think of this plot as a projection of all 1873 worlds onto our own solar system, with the Sun (and all other stars) at the far left. As you move out to the right, the orbital period of the planets increases, and correspondingly (thanks to Kepler’s Third Law), so does the distance from the star. Moving upwards means the mass of the worlds increase, from Moon-sized at the base to 10,000 times that of Earth at the top (30 Jupiter Masses).”
You’ll notice a few “clusters” as time moves along. The circles in dark blue are the planets in our Solar System; light blue are planets found by radial velocity. Then in maroon are planets found by direct imaging, followed by orange for microlensing and green for transits.
The first batch of exoplanets were the massive ‘Hot Jupiters’, which were the first exoplanets found “simply because they are easiest to find,” using the radial velocity method. Then you’ll see clusters found by the other methods ending with the big batch found by Kepler.
“This clustering shows that there are more Earth and super-Earth sized planets than any other,” said Osborn. “Hopefully we can begin to probe below it’s limit and into the Earth-like regime, where thousands more worlds should await!”
On reddit, Osborn also provided great, short explanations of the various methods used to detect planets, which we’ll include below:
Radial Velocity
Planets orbit thanks to gravitational attraction from their star’s mass. But the mass of the planet also has an effect on the star – pulling it around in a tiny circle once every orbit. Astronomers can split the light from a star up into it’s colours, which have an atomic barcode of absorption lines in. These lines shift position as the star moves – the light is effectively compressed to bluer colours when moving towards and pulled to redder colours when moving away.
So, by measuring this to-and-fro (radial) velocity, and finding periodic signals, astronomers can detect the tug of distant exoplanets.
Direct Imaging
This is easier to get your head around – point a big telescope at a star and directly image a planet around it. This only work for the biggest young planets as these are warmest, so glow brightest in the infra-red (like a red-hot piece of Iron). To find the planet in the glare of it’s star, the starlight needs to be suppressed. This is done by either blocking it out with a starshade, or digitally combining the images in such a way to remove the central star, revealing new exoplanets.
Microlensing
Einstein’s general theory of relativity shows that mass bends space time. This means that light can be bent by massive objects, and even act like a lens. Occasionally a star with a planetary system passes in front of a distant star. The light from the distant star is bent and lensed by both the star and the planet, giving two sharp increases in brightness over a few days – one for the star and one for the planet. The amount of lensing gives the mass of the planets, and the time between the events gives us the distance from their star. More info
Transits
When a planet crosses in front of it’s star, it blocks out a small portion of sunlight depending on it’s size. We only see the star as a single point, but we can infer the presence of a planet from the dip in light. When this repeats, we get a period. This is how we have found more than 1000 of the current crop of ~1800 exoplanets!
Thanks to Hugh Osborn for sharing his expertise with Universe Today!
Transit of Venus snapped from Princeton University at 6:19 p.m. June 5, 2012. This image was taken with a Questar telescope at 6:19 p.m. as the clouds over Princeton, NJ parted to the delight of hundreds of onlookers and whole families. Hundreds attended the Transit of Venus observing event organized jointly by Princeton University Astrophysics Dept and telescopes provided by the Amateur Astronomers Association of Princeton (AAAP), local astronomy club. Credit: Robert Vanderbei
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Despite a horrendous weather forecast, the clouds parted – at least partially – just in the nick of time for a massive crowd of astronomy and space enthusiasts gathered at Princeton University to see for themselves the dramatic start of the Transit of Venus shortly after 6 p.m. EDT as it arrived at and crossed the limb of the Sun.
And what a glorious view it was for the well over 500 kids, teenagers and adults who descended on the campus of Princeton University in Princeton, New Jersey for a viewing event jointly organized by the Astrophysics Dept and the Amateur Astronomers Association of Princeton (AAAP), the local astronomy club to which I belong.
See Transit of Venus astrophotos snapped from Princeton, above and below by Astrophotographer and Prof. Bob Vanderbei of Princeton U and a AAAP club member.
Transit of Venus snapped from Princeton University - full sized image
This photo was taken with a Questar telescope at 6:26 p.m. on June 5, 2012 - it’s a stack of eight - 2 second images. Stacking essentially eliminates the clouds. Hundreds attended the Transit of Venus observing event organized jointly by Princeton University Astrophysics Dept and telescopes provided by the Amateur Astronomers Association of Princeton (AAAP), local astronomy club. Credit: Robert Vanderbei
It was gratifying to see so many children and whole families come out at dinner time to witness this ultra rare celestial event with their own eyes – almost certainly a last-in-a-lifetime experience that won’t occur again for another 105 years until 2117. The crowd gathered on the roof of Princeton’s Engineering Dept. parking deck – see photos
Excited crowd witnesses last-in-a-lifetime Transit of Venus from campus rooftop on Princeton University. Onlookers gathered to view the rare Transit of Venus event using solar telescopes provided by the Amateur Astronomers Association of Princeton (AAAP) and solar glasses provided by NASA and lectures from Princeton University Astrophysics Dept.
Credit: Ken Kremer
For the next two and a half hours until sunset at around 8:30 p.m. EDT, we enjoyed spectacular glimpses as Venus slowly and methodically moved across the northern face of the sun as the racing clouds came and went on numerous occasions, delighting everyone up to the very end when Venus was a bit more than a third of the way through the solar transit.
Indeed the flittering clouds passing by in front of Venus and the Sun’s active disk made for an especially eerie, otherworldly and constantly changing scene for all who observed through about a dozen AAAP provided telescopes properly outfitted with special solar filters for safely viewing the sun.
Kids of all ages enjoy the Transit of Venus from a rooftop at Princeton University. Solar telescopes provided by the Amateur Astronomers Association of Princeton (AAAP), solar glasses provided by NASA and lectures from Princeton University Astrophysics Dept. Credit: Ken Kremer
As part of this public outreach program, NASA also sent me special solar glasses to hand out as a safe and alternative way to directly view the sun during all solar eclipses and transits through your very own eyes – but not optical aids such as cameras or telescopes.
Transit of Venus snapped from Princeton University - quarter sized image
This photo was taken with a Questar telescope at 6:26 p.m. on June 5, 2012 - it’s a stack of eight - 2 second images. Credit: Robert Vanderbei
Altogether the Transit lasted 6 hours and 40 minutes for those in the prime viewing locations such as Hawaii – from where NASA was streaming a live Transit of Venus webcast.
You should NEVER look directly at the sun through any telescopes or binoculars not equipped with special eye protection – because that can result in severe eye injury or permanent blindness!
We in Princeton were quite lucky to observe anything because other astro friends and fans in nearby areas such as Philadelphia, PA and Brooklyn, NY reported seeing absolutely nothing for this last-in-a-lifetime celestial event.
Transit of Venus enthusiasts view the solar transit from Princeton University rooftop using special solar glasses provided by NASA. Credit: Ken Kremer
Princeton’s Astrophysics Department organized a series of lectures prior to the observing sessions about the Transit of Venus and how NASA’s Kepler Space Telescope currently uses the transit method to detect and discover well over a thousand exoplanet and planet candidates – a few of which are the size of Earth and even as small as Mars, the Red Planet.
NASA’s Curiosity rover is currently speeding towards Mars for an August 6 landing in search of signs of life. Astronomers goal with Kepler’s transit detection method is to search for Earth-sized planets in the habitable zone that could potentially harbor life !
So, NASA and astronomers worldwide are using the Transit of Venus in a scientifically valuable way – beyond mere enjoyment – to help refine their planet hunting techniques.
Doing an outreach program for NASA, science writer Dr Ken Kremer distributes special glasses to view the transit of Venus across the sun during a viewing session on the top level of a parking garage at the E-quad at Princeton University to see the transit of Venus across the sun on Tuesday evening, June 5, 2012. Michael Mancuso/The Times
Historically, scientists used the Transit of Venus over the past few centuries to help determine the size of our Solar System.
See more event photos from the local daily – The Trenton Times – here
And those who stayed late after sunset – and while the Transit of Venus was still visibly ongoing elsewhere – were treated to an extra astronomical bonus – at 10:07 p.m. EDT the International Space Station (ISS) coincidentally flew overhead and was visible between more break in the clouds.
The International Space Station (ISS) flew over Princeton University at 10:07 p.m. on June 5 after the sun had set but while the Transit of Venus was still in progress. Credit: Ken Kremer
Transit Of Venus image from Hinode Spacecraft. Click to enlarge. Credit: JAXA/NASA/Lockheed Martin/enhanced by Marco Di Lorenzo
Of course clouds are no issue if you’re watching the Transit of Venus from the ISS or the Hinode spacecraft. See this Hinode Transit image published on APOD on June 9 and enhanced by Marco Di Lorenzo.
This week, local NY & NJ residents also had another extra special space treat – the chance to see another last-in-a-lifetime celestial event: The Transit of Space Shuttle Enterprise across the Manhattan Skyline on a seagoing voyage to her permanent new home at the Intrepid Sea, Air and Space Museum.
Four views of Endeavour docked to the ISS on May 29, 2011. Credit: Thierry Legault and Emmanuel Rietsch
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Award-winning French astrophotographer Thierry Legault traveled through Germany, France and Spain during Endeavour’s final mission to find clear skies and good seeing to capture the shuttle’s voyage to the International Space Station. While he told us it wasn’t easy, the results are incredible! The visible detail of the shuttle and parts of the International Space Stations is absolutely amazing. You can see the newly installed Alpha Magnetic Spectrometer in one shot, as well as the open payload bay doors on Endeavour in another. The video Legault shot is available on his website, and he has unique 3-D versions as well.
Below are some of his trademark views of transits of the Sun by ISS and Endeavour, with one showing the shuttle just before it docked to the station.
Solar transit taken on May 18th from Essen, Germany through thick clouds showing Endeavour a few minutes before docking to the ISS. Transit duration was 0.7 seconds. Credit: Thierry Legault.
Legault told us he was chasing the shuttle and the station from different parts of Europe, however because of weather problems (clouds and turbulence) he was not very happy with the results. But this image is stunning anyway even though clouds dimmed available light by more than 100 times, Legault said. What is perhaps most amazing is that the transit time for this pass in front of the Sun was 0.7 seconds!
Here’s a less cloudy view taken on May 25:
A close-up view of Endeavour and the ISS transiting the sun on May 25th from France. Transit duration was 0.5 seconds. Credit: Thierry Legault.
And the full view for reference. This transit was only a half second!
Solar transit taken on May 25th from France (Orleans), showing Endeavour docked to the ISS. Credit: Thierry Legault.
Series of transits taken on May 20, 22 and 23, 2011 from different areas of France, showing variations of orientation of the ISS with Endeavour docked. On May 23, the ISS passes besides a sunspot which is larger than the Earth. Credit: Thierry Legault
All transit images were taken with Takahashi TOA-150 6″ apochromatic refractor (focal length 2400mm and 3600mm) on EM-400 mount, Baader Herschel wedge. Nikon D3X at 1/8000s, 100 ISO, working in continuous shooting at 5 frames per second during 5 seconds.
Frames from videos taken from Spain (May 31) and France (June 1) 90 minutes before deorbit burn. Credit: Thierry Legault and Emmanual Rietsch.
Here are frames from videos taken by Legault and fellow astrophotographer Emmanual Rietsch just prior to the deorbit burn for landing on June 1. The video of these shots, as well as more images are also available on Legault’s website.
Thanks to Thierry for sending Universe Today these amazing images and allowing us to post them!
