Category: Astronomy

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The small constellation of Norma is located south of the ecliptic plane. It was originally charted by Abbe Nicolas Louis de Lacaille who named it “Norma et Regula”. It was later adopted by the International Astronomical Union as one of the 88 modern constellations and its name shortened to Norma. It covers approximately 165 square degrees of sky and ranks 77th in size. Norma has 2 main stars in its asterism and 13 Bayer Flamsteed designated stars within its confines. It is bordered by the constellations of Scorpius, Lupus, Circinus, Triangulum Australe and Ara. Norma is visible to all observers positioned at latitudes between +30° and ?90° and is best seen at culmination during the month of July.

The constellation of Norma has one annual meteor shower associated with it – the Gamma Normids. Activity begins on or about March 11 each year, lasting through March 21 with a peak date of March 16. This meteor shower only produces 5 to 9 meteors per hour at maximum and has only been studied within the last 50 years, so activity rates are sporadic and understudied.

Since Norma is considered a “new” constellation, there is no mythology associated with it – only Abbe Nicolas Louis de Lacaille’s love of all things science and what Norma is meant to represent. Originally named Norma et Regula, this dim collection of stars in Lacaille’s native language would have been “L’Équerre et La Règle”, meaning “The Set Square and The Ruler”. While it is difficult to visualize a set of drafting tools from this set of stars, Norma’s brighter stars do produce a few nice angles that will help guide you to some of its many deep sky riches.

Let’s start off our binocular tour of Norma with the “Y2” symbol on our map – Gamma 1 and Gamma 2 Normae. In a constellation which has no alpha or beta designations, fourth magnitude Gamma 2 is the brightest star here. The yellow giant star is located about 125 light years from Earth, but in binoculars you’ll notice another companion – Gamma 1. This is an optical double star because Gamma 1 is 1500 light years away!

For a true binary star, hop north to Epsilon Normae – the backwards “3” symbol on our map. Comprised of a 4.5 magnitude primary star and a 7.5 magnitude secondary, Epsilon is spaced widely enough apart to be split with steady binoculars and easily with a small telescope. Oddly enough, when it comes to this fixed position binary star, both components are also spectroscopic binary stars, too… Making this a quadruple star system!

Now, hop south for Iota 1 Normae – but bring a telescope. This 4.6 magnitude A7 subgiant star is located 271 light years from our solar system and its 11th magnitude companion has a close separation of 11″. This pair orbit each other very quickly, making a full revolution in just about 26 years.

Ready for a little variability? Then let’s start with Mu Normae – the “u” symbol. Mu is suspected of being an Alpha Cygni variable, with a magnitude range of 4.87 at brightest to a minimum of 4.98. This A type supergiant star doesn’t quite pulse like Cepheid – it exhibits non-radial pulsations during its brightness changes which may last from several days to several weeks! To follow a variable star whose changes are hugely apparent, take a look at R Normae. Here we have a Mira-type variable. It might take 507 for its changes to occur, but when they do, R will go from being an easy to spot in binoculars magnitude 6.5 to a need a telescope and star chart to find it magnitude 13.9!

Now, identify Kappa Normae – because it’s a guidestar to two awesome open clusters. In average 10X50 binoculars, if you place Kappa to the top of the field of view, you’ll easily see NGC 6067 (RA 16:13.2 Dec -54:13) to the north. Possessing about 100 stars spread in 13 arc minute field, this magnitude 5.6 cluster resolves beautifully in a telescope. It contains its share of Cepheid variables, too, but look for a wonderful bar-like structure with a concentration at one end. It’s bright, rich and very photogenic! Would you like to look at one more variable star?

With Kappa still at the top of your field of view, you’ll spy another open cluster to the south. Now, here’s a bonus, because you’ll find variable star S Normae locate right smack dab in the middle of open star cluster NGC 6087 (RA 16:18.9 Dec -57:54). At a combined magnitude of about 5.5, this galactic star cluster is meant for binoculars and telescopes of every size. At its heart beats S Normae, a well-known Cepheid that range in brightness from magnitude 6.1 to magnitude 6.8 magnitude every 9.75 days like clockwork. This particular cluster has been used as a cepheid calibrator to judge reddening influences down the main sequences in these type of clusters. Besides, it’s pretty!

A great mid-sized telescope object is open cluster NGC 6134 (RA 16:27:46 Dec -49:09:06). At around magnitude 7, this rich open cluster spans a generous 7 arc minutes and displays its stellar finery. Home to Delta-Scuti variables and rich in metal content, you’ll like this one, because it will give you an opportunity to look for a rare variable blue straggler star discovered there in 2001!

Larger telescopes are needed to spot NGC 6031 (RA 16:07:35.0 Dec -54:00:54.0) to the northwest of Kappa, though. Now approaching magnitude 9, this open cluster is far more sparsely arrange and definitely less populated. At around 2 arc minutes in size, this relatively young galactic cluster is nearly solar in its metal content and a nice challenge for your lists.

How about a challenging globular cluster? Then try your hand at NGC 5946 (RA 15:35:28.5 Dec -50:39:34). Located more than 34,000 light years from our Sun, this 10th magnitude globular was discovered on July 7, 1834 by John Herschel. At class IX, it’s a loose structure, but a great challenge. Why does it look like it has fallen apart? Maybe because it has. This particular one has undergone core collapse!

Last on our list for Norma is Collinder 299 (RA 16 18 42 Dec -55 07 00). This sparse open cluster will be hard to distinguish from the background stars, but use the lowest magnification you have available. We’re looking at a very old open cluster and one that has its stars chemically tagged along with other disk stars to help “unravel the dissipative history of the Galactic disk”.

There are many other great objects in Norma to have a look at, too… So grab a detailed star chart and get “normalized”….

Sources: SEDS, Wikipedia
Chart Courtesy of Your Sky.

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Ancient people have known about the planets since we were able to look up. Some stars were brighter than the rest, and seemed to move across the sky from night to night. These moving stars were known as planets, and there were 5: Mercury, Venus, Mars, Jupiter and Saturn. But the movements of the planets were puzzling to ancient astronomers. Some times the planets would slow down, go backwards, and then go forwards again. When a planet goes backwards, it’s called retrograde, and one of the best planets for this is Mercury. Let’s examine Mercury retrograde.

In ancient times, people thought the Earth was the center of the Universe, and all objects in the night sky orbited around us. One complication of this model was the planets which took these very predictable retrograde paths in their orbit. If the planets were orbiting the Earth, why would they go backwards? Why would Mercury go retrograde? They developed elaborate models where the planets followed a spiraling path around the Earth to account for this retrograde motion.

It wasn’t until Nicolaus Copernicus developed his Sun-centered model of the Solar System that the bizarre retrograde motion of Mercury and the rest of the planets finally made sense. The Earth is just another planet, and they’re all orbiting the Sun together. The retrograde motion of Mercury and the other planets is due to our relative positions in orbit.

So let’s understand retrograde motion, and look at what is Mercury retro in particular. The motion of the planets around the Sun follow the right-hand rule. Hold your right hand out, make a fist and stick the thumb up. The direction of the thumb points in the direction of the Sun’s northern pole. The curve of the fingers indicates the direction all the planets orbit around the Sun.

Mercury moves faster than the Earth as it travels around the Sun; however, Mercury has a highly elliptical orbit, so the speed of its orbit changes. When Mercury is furthest from the Sun, it’s at the slowest point in its orbit, and this gives the Earth a chance to “catch up”. Imagine you’re driving next to a car in the freeway which is speeding up and slowing down. It’s still going down the highway at a high speed, but it seems to be going back and forth compared to you. When this happens, astronomers say that Mercury is in retrograde.

Astrologers seem to think that retrograde motion is an unlucky or bad situation because it goes against a planet’s natural movements. Of course, the planet isn’t really changing its motions at all, it’s only our perspective of the planet that’s changing. Furthermore, at any one time, 40% of the outer planets are in retrograde motion anyway. Something’s almost always in retrograde.

Is Mercury in retrograde right now? It depends on the date. Check the list of dates below to check.

So when is Mercury going to be in retrograde? Here are some Mercury retrograde dates for the next few years.

Mercury Retrograde 2009

• January 11-31
• May 6-20
• September 6-29
• December 26-January 15, 2010

Mercury Retrograde 2010

• April 17-May 11
• August 20 – September 12
• December 10-December 29

Mercury Retrograde 2011

• March 30-April 23
• August 2 – August 26
• November 23 – December 13

Mercury Retrograde 2012

• March 11-April 4
• July 14 – August 7
• November 6 – November 26

Here’s a link to the 2009 mercury retrograde dates.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Mercurio retrógrada

References:
NASA: Planetary Motion
NASA Astronomy Picture of the Day
NASA: Mercury

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Mercurian world is one of extremes. 700 Kelvin on the side exposed to the Sun, yet some areas are never exposed to sunlight and are as cold as deep space. Scientists do not believe there has ever been life on Mercury. The atmosphere on Mercury is almost non-existant. It doesn’t protect the planet from the harsh radiation of the Sun or radiation from space, nor does it trap heat and provide a breathable atmosphere. Mercury is inhospitable and sterile.

In order for life (as we know it) to exist, Mercury would need to have temperatures that allow liquid water to remain on its surface for long periods of time. But the temperatures on Mercury extend from just above absolute zero when the surface is shadowed to 700 Kelvin when its in sunlight. Liquid water just can’t exist in that kind of environment.

Any ancient life on Mercury would have faced many extinction events. Here on Earth many past life forms have been destroyed by asteroid impacts. The dinosaurs are a classic example. Images of Mercury’s surface returned by the Mariner 10 and MESSENGER spacecraft have shown that the surface has suffered many large impacts. In fact, it was heavily bombarded during the Late Heavy Bombardment that occurred about 3.9 billion years ago. Any one of those impacts could have destroyed any life on the planet. Many scientists believe that a great deal of the planet’s surface was stripped away by one impact. If the impact removed a large portion of the surface, surely it would have taken any life that existed at the time with it.

All evidence that science has do date indicates that there has never been life on Mercury and never will be. The harsh conditions on the planet’s surface and the tenuous atmosphere make it impossible for any life form known to man to exist.

But there are other planets in the Solar System. Here’s an article about life on Pluto, and here’s one about life on Mars.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Vida sobre el mercurio

References:
NASA Solar System Exploration: Mercury
Wikipedia
JAXA: Mercury Quantities
NASA MESSENGER Mission
NASA Multimedia

Neptune is the most distant planet from the Sun, with temperatures that plunge down to 55 Kelvin, or -218 degrees Celsius. You would think that a planet that cold would be frozen and locked down, with very little weather. But you’d be very wrong. In fact, the weather on Neptune is some of the most violent weather in the Solar System.

Just like Jupiter and Saturn, Neptune has bands of storms that circle the planet. While the wind speeds on Jupiter can reach 550 km/hour – twice the speed of powerful hurricanes on Earth, that’s nothing compared to Neptune. Astronomers have clocked winds on Neptune traveling at 2,100 km/hour.

So why can the winds on Neptune reach such huge speeds? Astronomers think that the cold temperatures on Neptune might have something to do with that after all. The cold temperatures might decrease the friction in the system, so that winds can get going fast on Neptune.

During its 1989 flyby, NASA’s Voyager 2 spacecraft discovered the Great Dark Spot on Neptune. Similar to Jupiter’s Great Red Spot, this is an anti-cyclonic storm measuring 13,000 km x 6,600 km across. A few years later, however, the Hubble Space Telescope failed to see the Great Dark Spot, but it did see different storms. This might mean that storms on Neptune don’t last as long as they do on Jupiter or even Saturn.

The more active weather on Neptune might be due, in part, to its higher internal heat. Although Neptune is much more distant than Uranus from the Sun, receiving 40% less sunlight, temperatures on the surface of the two planets are roughly similar. In fact, Neptune radiates 2.61 times as much energy as it receives from the Sun. This is enough heat to help drive the fastest winds in the Solar System.

We have written many articles about Neptune for Universe Today. Here’s an article about how Neptune’s south pole is the warmest part of the planet, and here’s more information about the atmosphere on Neptune.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.

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To really understand how big Neptune really is, you need some kind of comparison. Let’s see how Neptune compares to Earth in every way.

First, let’s just look at pure size. The diameter of Neptune is approximately 49,500 km. This makes Neptune the 4th largest planet in the Solar System. And compared to Earth? Neptune is 3.9 times bigger.

Now mass. The mass of Neptune is 1.02 x 10²⁶ kg. If you wanted to write it out, it would be 102,000,000,000,000,000,000,000,000 kg. Neptune has 17 times as much mass compared to the Earth.

How about volume? The volume of Neptune is 6.3 x 10¹³ km³. You could fit 57 Earths inside Neptune and still have room to spare.

A day on Earth is 24 hours, but a day on Neptune is 16 hours and 6 minutes. A year on Earth is, um, 1 year obviously, while a year on Neptune is 164.79 years.

Here’s one element that’s actually pretty close. The surface gravity on Neptune (if it actually had a surface that you could stand on) is only 14% stronger than the pull of gravity on Earth. You would have a difficult time noticing if you were standing on the surface of Neptune compared to the surface of Earth.

We have written many articles about Neptune for Universe Today. Here’s an article about three new trojan asteroids found in Neptune’s orbit, and a possible mission to Neptune under study.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.

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Neptune orbits the Sun at an average distance of 4.5 billion km.

That’s the simple answer to the question, what is the orbit of Neptune. However, things are actually a little more complicated than that. Like all the planets in the Solar System, Neptune follows an elliptical path around the Sun, varying its distance to the Sun at different points along its orbit.

At its closest point in its orbit, which astronomers call perihelion, Neptune gets within 4.45 billion km, or 29.77 astronomical units (1 astronomical unit or AU is the average distance of the Earth to the Sun).

At its most distant point in its orbit, called aphelion, Neptune reaches a distance of 4.55 billion km, or 30.44 astronomical units.

One interesting feature about the orbit of Neptune is the fact that Pluto’s very elliptical orbit sometimes brings it closer to the Sun. Back in the days when Pluto was still a planet, it would spend a few decades every orbit closer to the Sun. So Neptune was actually the most distant planet, and Pluto was closer. The last time this happened started in 1979, and ended in 1999. Of course, Pluto isn’t a planet any more, so Neptune’s orbit makes it the most distant planet.

We have written many article about Neptune on Universe Today. Here’s an article with images of Neptune captured by the Hubble Space Telescope. And here’s another discussing the planet’s relatively warm south pole.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.