The Atmosphere of Pluto

One of the most amazing parting shots of the planet Pluto, backlit by our distant Sun. Taken by the New Horizons probe as it rushed away from the planet in 2015. Look closely and Plutonian mountains can be seen casting long shadows through the hazy blue atmosphere.

As of now Pluto is the only trans-Neptunian object with a known atmosphere.

Image credit @nasa

Moon Formation

Modelling suggests the Earth came very close to having a pair of smaller Moons.

According to simulations by Canup and Ida (2014) the Earth came very close to hosting two smaller Moon’s (right) rather than the large single Moon we ended up with (left).

This fascinating ‘what if’ modelling is based on the giant impact hypothesis. A faster rate of rotation of the post impact disk is the main requirement for a two Moon system to take hold.

Of course multiple moon system are very common. Saturn for example has an abundance of them, with the most recent count totalling 82 orbiting bodies.

Colour Image: Artist’s impression of an alien world with two moons by Angela Harburn.

Mercury and Maximum Elongation

I hope you enjoy this short video about the planet Mercury, which you can currently see during late evening, low on the NW horizon. Mercury is also approaching its maximum evening elongation on the 17th May.

Joining me once again is Steve Owens, astronomer at Glasgow Science Centre and author of Stargazing For Dummies.

In this video podcast we discuss:

1. Tips for observing Mercury safely.

2. Mercury’s phases.

3. The surface geology of Mercury and how this reveals tantalising hints about its history and formation.

Venus & Mercury

While I shivered this morning trying to find Mercury amidst a blanket of freezing cold mist, Lynsey Gibson fortuitously snapped it from the cozy confines of her bed.

The bright object in the first image is actually the planet Venus, her intended target, but if you zoom in Lynsey’s phone snap has also picked up Mercury. See the second image which I’ve annotated.

This is a great example of how much fainter Mercury is compared to Venus (I usually use binoculars to help locate it) and the power and versatility of smartphone cameras.

Thanks for the share again Lynsey and clear skies everyone.

Mars at Opposition

Collage by Instagram’s @NightSkyFlying

Have you noticed the dazzling red star high in the East during late evening? That’s the planet Mars and it’s now nearing opposition on October 13th, offering some of the best naked eye and telescopic views possible.

Opposition is when Mars and Earth reach their closest approach to each other with respect to their independent orbits around the Sun. For Mars and Earth, this happens every 2 years and 2 months.

With the planet’s relatively high altitude and closeness around opposition, current views of the planet even with moderately powerful telescopes should be striking, perhaps revealing dim surface features and polar caps.

These images from Instagram’s @nightskyflying show the dramatic size and clarity change of Mars over a period of many months. If you don’t have a telescope it’s still worth looking up to appreciate the brightness of Mars as a naked eye planet at the moment.

Image by @NightSkyFlying

Signs of Microbial Life on Venus?

All eyes are now on planet Venus, our bright morning and evening star.

In the 1950s Venus was one of the most dreamed of and speculated about planets in the solar system. Science fiction portrayed it as a swampy planet covered in rain forests and abundant with strange alien life. Then, after the Soviet Venera missions discovered the hellish conditions on the surface, interest waned somewhat and attention shifted to Mars.

With recent discoveries of Phosphine gas in the planet’s atmosphere, Venus looks set to recapture all of its human wonder and fascination.

Venus has always had the potential to harbour life high in its atmosphere. While its surface is baking hot with crushing pressures, its upper atmosphere is a relatively warm and clement environment.

So far we can’t imagine a natural process which could produce such high concentrations of phosphine gas in the Venus atmosphere but that doesn’t mean there isn’t an explanation that precludes life. Meanwhile we are left to speculate about the many possibilities, including the most tantalising of all, that some form of ancient anaerobic microbial life exists, or has existed, within Venus’s upper atmosphere.

An Alien Solar System

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A direct image of an alien solar system orbiting a Sun like star, over 300 light years away!

I remember growing up in the 1980s hearing about the ‘high probability’ that other stars had orbiting planets, but there was very little evidence then, only some tantalising hints from the gravitational wobbles observed from specific stars.

Since then thousands of new exoplanets have been confirmed using the transit and radial velocity detection methods. I wrote a blog article about this a while back.

These methods are indirect ways of determining the existence of planets, and it’s very rare to actually be able to ‘see’ the planets themselves.

This image is therefore pretty incredible and for me suddenly normalises the idea that these star systems are real places we could, theoretically at least, visit in the distant future.

The image was captured by the European Southern Observatories Very Large Telescope and shows a young Sun like star (only 17 million years old) with two clearly defined giant planets in orbit. (The dots of light closer to the star are background stars and therefore not part of this particular planetary system)

These planets orbit the star at 160 and 320AU (1 AU is the Earth to Sun distance) so they’re much further away from the star than any planet in our solar system.

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