We noticed you're browsing in private or incognito mode.

To continue reading this article, please exit incognito mode or log in.

Not an Insider? Subscribe now for unlimited access to online articles.

Emerging Technology from the arXiv

A View from Emerging Technology from the arXiv

The Puzzle of Astronomy's Unexplained Anomalies

A series of mysterious observations of objects within the solar system could indicate the existence of exotic new physics.

  • July 29, 2009

At the end of the 19th century, astronomers discovered that the perihelion of Mercury (its closest point to the sun during its orbit) was slowly advancing in a way that could not be explained by Newtonian physics. The anomaly was small, so tiny that most believed that a simple explanation would soon be found. It turned out, of course, that Mercury’s orbit was a clue to the existence of an entirely new physics concept, called general relativity, which fundamentally changed our understanding of the universe.

If there’s a lesson there, it is to pay attention to small anomalies.

Which is why a list prepared by John Anderson at the Jet Propulsion Laboratory in California and Michael Nieto at Los Alamos National Laboratory in New Mexico makes for interesting reading. The two scientists have compiled details on four unexplained anomalies that astronomers are currently scratching their heads over (I’ve added a fifth). Let’s take a look.

1. First up is the flyby anomaly, which we’ve discussed on the arxivblog here, here, and here. This is the discovery that spacecraft flying past Earth experience a small but significant change in acceleration, an effect that has been studied in detail by Anderson and shown to be real rather than an artifact of some kind.

2. Next is the slow but sure increase in the length of the astronomical unit (AU), a unit of measure roughly equal to the mean distance from Earth to the sun. This has been calculated as 149,597,870,700 meters, plus or minus three meters, and it is by far the most accurately determined constant in astronomy, the data coming from distance measurements between Earth and various Mars orbiters and landers dating from 1976 to the present. However, these data indicate that the AU is increasing by about 15 centimeters per year.

One explanation is that the mass of the sun is increasing (there is a mathematical relationship linking the AU to the mass of the sun). In fact, the mass of the sun ought to be decreasing because of mass loss to solar radiation and the solar wind. To explain the increase in the AU, the sun would have to be increasing its mass by 10^18 kilograms per year. That’s equivalent to swallowing a good-sized planetary moon or about 40,000 comets per year. Surely we’d have noticed that.

3. Then there is the Pioneer anomaly, the small but steady slowing of the Pioneer spacecraft as they move out of the solar system. Nobody has been able to satisfactorily explain what’s pulling them back, although there has been no shortage of attempts.

4. Finally, Anderson and Nieto point to the increase in eccentricity of the moon’s orbit, as measured by laser-ranging measurements between 1970 and 2008. These data show that the moon’s apogee and perigee have increased in distance by about 3.5 millimeters per year.

5. Anderson and Nieto could add a fifth puzzle to their list: the recent anomalies measured in Saturn’s orbit.

Does that add up to evidence for new physics, or just a poor application of the physics we do know? Whatever the answer, these are problems worth watching.

Ref: arxiv.org/abs/0907.2469: Astrometric Solar-System Anomalies

Want to go ad free? No ad blockers needed.

Become an Insider
Already an Insider? Log in.
Want more award-winning journalism? Subscribe to Insider Basic.
  • Insider Basic {! insider.prices.basic !}*

    {! insider.display.menuOptionsLabel !}

    Six issues of our award winning print magazine, unlimited online access plus The Download with the top tech stories delivered daily to your inbox.

    See details+

    Print Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

You've read of three free articles this month. for unlimited online access. You've read of three free articles this month. for unlimited online access. This is your last free article this month. for unlimited online access. You've read all your free articles this month. for unlimited online access. You've read of three free articles this month. for more, or for unlimited online access. for two more free articles, or for unlimited online access.