Faculty Forum - What's Happening in Astronomy?

Planet Nine

Planet Nine

Earlier this year, astronomers proposed a ninth planet for our solar system, and it’s not Pluto. Michael Brown and Konstantin Batygin of Caltech believe there is a massive planet orbiting the sun in an ellipse that, at aphelion (the furthest point in the orbit), possibly extends more than 1,000 Astronomical Units (AU) from the sun. One AU is the distance between the sun and the Earth, or about 93 million miles.

Brown has previously discovered other significant objects, such as Sedna in 2003 and Eris in 2005, in distant regions of the solar system called the Kuiper Belt and the even more remote Oort Cloud. It was discoveries such as these that prompted the International Astronomical Union (IAU) in 2006 to define planets in a way that expelled Pluto, a demotion favored by Brown.

In 2014, Chadwick Trujillo and Scott Sheppard published a paper regarding an inner Oort Cloud object, 2012 VP113, with its perihelion (the closest point in the orbit) at approximately 80 AU. More significantly, though, in their discussion they suggested a potential super-Earth-mass body to be a gravitational perturber and had mathematically simulated the effects of such at 250 AU. Brown and Batygin set out to disprove this hypothesis but instead found evidence that supported Trujillo and Scott. In a January 2016 paper published in The Astronomical Journal, “Evidence for a distant planet in the solar system,” they too proposed a massive gravitational perturber, a new planet, which is responsible for the orbital paths of numerous other bodies in this region of the solar system.

The orbits of a number of bodies were found to cluster at perihelion, having similar ellipses tilted 30 degrees in the same direction with regard to the eight main planets.

This was given only a 0.007% chance of occurring without the gravitational influence of a significantly more massive object. These orbits were found to be explainable by the influence of a distant planet with a mass more than 10 times the mass of the Earth. Such a planet could also give reason for the orbits of certain other Sedna-like objects beyond Neptune in the Kuiper Belt.

If verified, the IAU will officially name the new planet according to established criteria. For now, though, Batygin and Brown have nick-named the body “Planet Nine” and have set out to find it. Its orbit is roughly known but not its position on that orbit – an ellipse potentially so large that it could take the planet as many as 20,000 Earth-years to circle the sun just once. The massive planet would be the fifth largest in our solar system, after Jupiter, Saturn, Uranus and Neptune. It is thought to be icy and rocky, and it may contain a small gaseous atmosphere. Its orbit could take it as many as 155 billion miles from the sun.

Pluto is not massive enough to have the gravitational force necessary to clear its orbit of other objects, one of the primary characteristics necessary to be a planet. Planet Nine, though, at 5,000 times the mass of Pluto, will clear its path, changing the orbits of other objects while gravitationally dominating its part of the solar system. When confirmed, this will give us a ninth planet once more.

Brown has since added that the six-degree tilt of the orbital plane of the eight main planets has finally been explained by the existence of Planet Nine. He says that at its distance the planet’s gravitational force acts as a great lever arm that has gradually tilted the other planets in its direction.

Brown is confident that Planet Nine exists and states that it will definitely meet all planetary criteria. He and Batygin continue their search but also hope that their publication of what they have determined so far will inspire other astronomers at some of the most powerful telescopes to search as well. Brown would like to make the confirmation himself, but even more so he simply wants Planet Nine to be found by someone. He thinks that may happen by the end of next winter.

The Great Solar Eclipse of 2017

solar eclipseMark your calendars! There will be a total eclipse of the sun viewable in parts of the United States on August 21, 2017.

Total solar eclipses are infrequent and are visible in any geographical area only rarely. The last one in the continental United States occurred approaching 38 years ago in 1979, and even then the viewing area was very limited. This time the shadow of the moon being cast upon the Earth will enter the United States on the Pacific coast near Salem, Oregon, and will arc across the country passing by Kansas City and St. Louis on its way to Charleston, South Carolina, and the Atlantic. You can search online for an eclipse map that will show the path of totality’s nearest point to you. Many people pay thousands of dollars to travel around the world in order to see a total eclipse. This time, however, the eclipse is close to home—for those in Oklahoma it is simply a ride up Interstate 44 to the near side of St. Louis.

Solar eclipses occur when the moon in its orbit is in perfect alignment between the sun and the Earth. Due to orbital inclinations this may happen only once or twice a year, if that, and then the shadow will normally be seen only across a relatively small area. Sometimes this area is over one of the oceans, which is when people will book passage on ships positioning themselves for the spectacular sight. The width of the path of totality (the shadow of the moon on the Earth) for the upcoming eclipse will be about 67 miles wide.

In the area approaching St. Louis, totality will begin in the afternoon at approximately 1:15 p.m. Depending on how close to the centerline of totality it is from where one is viewing, darkness will last for up to about two minutes and 40 seconds. Along Interstate 44 the centerline passes through St. Clair, Missouri, but briefer periods of totality will be visible from east of Rolla almost to downtown St. Louis. Darkness sets in quickly and confuses birds and insects. The sun will be covered by the black disc of the moon, but a halo will be visible as the sun’s corona emanates from the edges. Stars will become visible in the middle of the day. Partial phases of the eclipse will begin more than an hour before totality and will last for more than an hour after.

To avoid permanently damaging one’s eyes, it is important not to look into the blinding rays of the sun without protective goggles designed specifically to filter out the sun’s ultraviolet and infrared rays. One may also use an averting device. One such source of information may be found at www.eclipseglasses.com

Make plans now to witness this rare and fantastic event! Hotel rooms are already filling up, but some may still be available. If necessary, one can always find a room outside of the area of totality and drive in for the spectacle. It is a “bucket list” experience that one should not miss!

The Scale of the Universe

scale of universeWe live in the Milky Way Galaxy, a galaxy in which our sun is only one of well more than 100 billion other stars. In addition to this, astronomers had believed there to be as many as 200 billion other galaxies in the universe, each with its own vast star populations. Christopher Conselice, of the University of Nottingham in England, and a team of astrophysicists, however, have now determined there to be far more than previously thought—at least two trillion galaxies! The team used sky surveys made by the Hubble Space Telescope and other large instruments for three-dimensional modeling that enabled them to arrive at this number.

Conselice states that the number could be even greater. Low-mass galaxies were the first in the universe and these are what are now being discovered. The Hubble will be replaced in 2018 by the far more powerful James Webb Space Telescope that will be able to readily study these low-mass galaxies that are now just barely detectable.

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Steven Gullberg, Ph.D.

Dr. Steve Gullberg is an Assistant Professor of Interdisciplinary Studies and Aviation for the University of Oklahoma College of Professional and Continuing Studies. He is a retired airline captain, a long-time adjunct instructor for the College of Professional and Continuing Studies, and an active member in the International Astronomical Union.