Chilly as winter may feel in the Northern Hemisphere, we are more than 3 million miles closer to our fiery star than we were in the dead of summer.

The change in distance occurs because our planet’s orbit is stretched into an ellipse — so Earth snuggles up to the Sun every January and dips farther into the outer solar system every July, at a point known as aphelion.

Although 3 million miles sounds vast, it’s not much on the scale of our solar system. In fact, despite the planet’s elliptical path through the heavens, most astronomers say that Earth’s orbit is basically circular. On a scale of 0 to 100 percent, where 0 is a circle and nearly 100 is a very thin oval, Earth only scores a 1.7. It is a defining trait that keeps our planet at roughly the same distance from our sun, and keeps the climate relatively stable.

Marburg virus is found in West Africa

The Marburg virus, a deadly cousin of Ebola, has been isolated in fruit bats in Sierra Leone, marking the first time it has been found in West Africa.

Five Egyptian rousette fruit bats caught in three health districts tested positive for the virus, according to a team led by the Centers for Disease Control and Prevention and Sierra Leone’s Njala University, and a second by the University of California, Davis, and Sierra Leone’s University of Makeni.

The testing was done as part of a U.S.-led effort to spot pathogens lurking in animals and take steps to prevent them from crossing over into humans and triggering lethal outbreaks. Known as Predict, the effort is paid for by the U.S. Agency for International Development.

The bats shed the virus in their feces, urine and saliva. Humans may get the virus from being bitten when they capture bats to eat, from cuts during food preparation or from infectious bat guano. The largest known outbreak of Marburg virus, which began in Angola in 2004, sickened over 250 people and had a 90 percent fatality rate. Two of the strains found in Sierra Leone bats were similar to the Angolan ones.

Massive rock may have hit Uranus

Uranus is a lopsided oddity, the only planet to spin on its side. Scientists now think they know how it got that way: It was pushed over by a rock at least twice as big as Earth.

Computer simulations show that an enormous rock crashed 3 billion to 4 billion years ago into the seventh planet from the sun, said Durham University astronomy researcher Jacob Kegerreis.

Uranus tilts about 90 degrees on its side, as do its five largest moons. Its magnetic field is also lopsided and doesn’t go out the poles like ours does, said NASA chief scientist Jim Green. It’s possible that the object that knocked over Uranus is still lurking in the solar system too far for us to see, said Green. It would explain some of the orbits of the planet and fit with a theory that a missing planet X is well beyond Pluto, he said.