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Image: Artist's impression of star system. Credit: ESO/M. Kornmesser/spaceengine.org

This artist’s impression shows the view from the surface of one of the planets in the TRAPPIST-1 system. At least seven planets orbit this ultra cool dwarf star 40 light-years from Earth and they are all roughly the same size as the Earth. They are at the right distances from their star for liquid water to exist on the surfaces of several of them. This artist’s impression is based on the known physical parameters for the planets and stars seen, and uses a vast database of objects in the Universe. Credit: ESO/M. Kornmesser/spaceengine.org

 

Astronomers have found a system of seven Earth-sized planets just 40 light-years away. Using ground and space telescopes, including ESO’s Very Large Telescope, the planets were all detected as they passed in front of their parent star, the ultracool dwarf star known as TRAPPIST-1. According to the paper appearing today in the journal Nature, three of the planets lie in the habitable zone and could harbor oceans of water on their surfaces, increasing the possibility that the star system could play host to life. This system has both the largest number of Earth-sized planets yet found and the largest number of worlds that could support liquid water on their surfaces.

Astronomers using the TRAPPIST–South telescope at ESO’s La Silla Observatory, the Very Large Telescope (VLT) at Paranal and the NASA Spitzer Space Telescope, as well as other telescopes around the world, have now confirmed the existence of at least seven small planets orbiting the cool red dwarf star TRAPPIST-1. All the planets, labelled TRAPPIST-1b, c, d, e, f, g and h in order of increasing distance from their parent star, have sizes similar to Earth.

Dips in the star’s light output caused by each of the seven planets passing in front of it — events known as transits — allowed the astronomers to infer information about their sizes, compositions and orbits. They found that at least the inner six planets are comparable in both size and temperature to the Earth.

Lead author Michaël Gillon of the STAR Institute at the University of Liège in Belgium is delighted by the findings: “This is an amazing planetary system — not only because we have found so many planets, but because they are all surprisingly similar in size to the Earth!”

With just eight percent the mass of the Sun, TRAPPIST-1 is very small in stellar terms — only marginally bigger than the planet Jupiter — and though nearby in the constellation Aquarius (The Water Carrier), it appears very dim. Astronomers expected that such dwarf stars might host many Earth-sized planets in tight orbits, making them promising targets in the hunt for extraterrestrial life, but TRAPPIST-1 is the first such system to be found.

Co-author Amaury Triaud expands: “The energy output from dwarf stars like TRAPPIST-1 is much weaker than that of our Sun. Planets would need to be in far closer orbits than we see in the Solar System if there is to be surface water. Fortunately, it seems that this kind of compact configuration is just what we see around TRAPPIST-1!”

The team determined that all the planets in the system are similar in size to Earth and Venus in the Solar System, or slightly smaller. The density measurements suggest that at least the innermost six are probably rocky in composition.

The planetary orbits are not much larger than that of Jupiter’s Galilean moon system, and much smaller than the orbit of Mercury in the Solar System. However, TRAPPIST-1’s small size and low temperature mean that the energy input to its planets is similar to that received by the inner planets in our Solar System; TRAPPIST-1c, d and f receive similar amounts of energy to Venus, Earth and Mars, respectively.

All seven planets discovered in the system could potentially have liquid water on their surfaces, though their orbital distances make some of them more likely candidates than others. Climate models suggest the innermost planets, TRAPPIST-1b, c and d, are probably too hot to support liquid water, except maybe on a small fraction of their surfaces. The orbital distance of the system’s outermost planet, TRAPPIST-1h, is unconfirmed, though it is likely to be too distant and cold to harbor liquid water — assuming no alternative heating processes are occurring. TRAPPIST-1e, f, and g, however, represent the holy grail for planet-hunting astronomers, as they orbit in the star’s habitable zone and could host oceans of surface water.

These new discoveries make the TRAPPIST-1 system a very important target for future study. The NASA/ESA Hubble Space Telescope is already being used to search for atmospheres around the planets and team member Emmanuël Jehin is excited about the future possibilities: “With the upcoming generation of telescopes, such as ESO’s European Extremely Large Telescope and the NASA/ESA/CSA James Webb Space Telescope, we will soon be able to search for water and perhaps even evidence of life on these worlds.”

Closed for the season

StephensAstro —  December 23, 2016 — Leave a comment

Photo: Stephens Memorial Observatory - December 2016. Photo by James Guilford.

Stephens Memorial Observatory – December 2016


 
In our previous post we explained the reasons for not scheduling a December Open Night this year. As it turned out, the most likely date the public event would have occurred would have been December 17 and, unsurprisingly, the weather that night was awful! So, today we bundled up the big telescope for a long winter’s nap and, unless we are blessed with stretches of clear nights with tolerable temperatures in January and February, we won’t open to the public until March 2017.

Our best wishes to everyone for a happy holiday season and a peaceful and productive new year!

No December open night

StephensAstro —  December 12, 2016 — Leave a comment
Photo: Christmas Tree Cluster

This color image of the region known as NGC 2264 is an area of sky that includes the sparkling blue baubles of the Christmas Tree star cluster and the Cone Nebula. Image Credit: ESO

Well we give up! The skies and the calendar just are not coming into alignment for a December Open Night! Clouds and inclement weather (of various temperatures) are making stargazing impossible and have been plaguing us quite often this season. And there’s no way we would schedule a public event for Christmas Eve!

So we’ll say thanks for your interest and hope more clear skies come our way next year.

Normally at this point we bundle up the telescope for the winter and schedule nothing until March. If, however, the weather presents us with sufficient notice of good observing chances we may just present a “pop-up” Open Night before spring. We would love to show off the Orion Nebula through the old scope! Watch our Twitter feed and/or check back here after the holidays for any surprises.

At any rate, we hope you will have a safe and warm winter and a wonderful new year. For those who observe it, happy Christmas to you!

And for everyone, here is a beautiful image of the Christmas Tree star cluster, provided by the European Southern Observatory (ESO) to help make the season bright. Enjoy!

Photo: Nearly Full Perigee (aka "supermoon")  - November 13, 2016, 5:52 PM. Photo by James Guilford.

Shortly After Rising: Nearly Full Perigee (aka “supermoon”) Moon – November 13, 2016, 5:52 PM

We’ve said it before, usually too much is made of so-called “supermoon” occasions; they happen with fair regularity and have little astronomical significance, and an astrologer invented the term.

Supermoons are also known as perigee Full Moons — times when Earth’s Moon reaches its full phase and the low point in its orbit (closest to Earth) at the same time. Our Moon is on an elliptical orbit that carries it nearer and farther from Earth, the distance constantly changing as it travels along its path. Perigee Full Moons, because they are somewhat closer to Earth, mean the Moon looks bigger, brighter, and will have an increased influence on ocean tides.

Tonight’s Full Moon, however, may just deserve the supermoon moniker: it will be the closest Full Moon since 1948, floating 221,524 miles (356,509 km) away. We won’t have another perigee Full Moon so close until 2034.

Technically, the Moon reaches perigee (low point in an orbit) tomorrow morning. According to an article from NASA, “The biggest and brightest Moon for observers in the United States will be on Monday morning just before dawn. On Monday, Nov. 14, the moon is at perigee at 6:22 a.m. EST and “opposite” the sun for the full moon at 8:52 a.m. EST (after moonset for most of the US).” The farthest our Moon traveled from us this year was to an apogee (high point of orbit) of 252,688 miles on October 31.

Tonight’s Moon will be brilliant, as it is every time it reaches Full, but many folks won’t really notice the 14 percent larger appearance and 30 percent difference in brightness. Still, the interest is good and our amazing and beautiful nearest neighbor in space deserves the appreciation!

Due to scheduling difficulties, there will be no November Open Night at the observatory. We regret we are unable to offer a program this month but hope to offer public observing in December. Thank you for your interest!

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UPDATE: Only a handful of guests visited – too much competition from sports events – but those who came had superb views of Moon, good views of the Andromeda Galaxy and Perseus Double Cluster later.

Stephens Memorial Observatory of Hiram College will be open for public observing Saturday, October 8, from 7:00 to 9:00 PM. Focus of the night will be Earth’s Moon and part of this year’s International Observe the Moon Night.

International Observe the Moon Night (InOMN) is an annual worldwide public event that encourages observation, appreciation, and understanding of our Moon — the same moon seen around the world by all people.

While the Moon will be the “star” of the night, other night sky gems may also be offered for viewing through the observatory’s large vintage telescope.

No reservations are required and there is no admission fee for observatory public nights. Cloudy skies at the starting time cancel the event and, in that case, the observatory will not open.

The Observatory is located on Wakefield Road (Rt. 82) less than a quarter of a mile west of Route 700 in Hiram. There is no parking at the Observatory. Visitors may park on permissible side streets near the Post Office, a short distance east of the observatory.

Tonight’s planned Public Night is CANCELED due to inclement weather conditions and overcast skies expected to continue into late-night.