It's a new era for investors hoping to get in on the bitcoin game.

Cboe Global Markets, a top U.S. owner of financial exchanges, on Sunday began offering bitcoin futures, allowing investors to speculate on whether the digital currency's price will go up or down.

In the first few hours, most were betting that bitcoin, which has experienced a spectacular rally this year, will rise even higher.

It's the first time a government-regulated exchange has given the green light to trading for a bitcoin-backed security.

Chicago-based Cboe tweeted Sunday that its website was receiving "heavy traffic" after trading began. But it also added that all trading systems were "operating normally."

Due to heavy traffic on our website, visitors to https://t.co/jb3O722hoo may find that it is performing slower than usual and may at times be temporarily unavailable. All trading systems are operating normally. — Cboe (@CBOE) December 10, 2017

The start of trading was a historic move. Unlike traditional commodities, bitcoins aren't physical assets. And unlike traditional currencies, there isn't a central bank that backs bitcoin.

Bitcoins live on computer servers. They are produced by complex algorithms and recorded in a digital ledger.

Related: I bought $250 in bitcoin. Here's what I learned

Bitcoin, whose price has soared roughly 1,500% since the start of the year, got a lift from the new activity on the Chicago exchange.

It jumped about 8% in less than 10 minutes -- to more than $15,700 -- after the futures trading began, according to data from CoinDesk, which values bitcoin based on data from four exchanges.

By late Sunday, it was trading above $16,000. And on the futures exchange, contracts expiring next month were trading above $18,000.

Some leading economists and financiers are calling bitcoin a bubble and a fraud, but industry insiders say they think it's only going to get bigger as it gains more widespread acceptance.

Related: History's biggest bubbles never end well

Currently, bitcoins are bought and sold on unregulated virtual exchanges -- and it's been extremely volatile.

Last week, in the run-up to its futures trading debut, bitcoin's value soared on some exchanges from less than $10,000 to $17,000 before dropping back to near the $15,000 mark, spurring renewed warnings of a bubble.

Stephen Bielecki, an attorney with Kleinberg Kaplan, told CNNMoney this weekend that offering bitcoin futures may help "rationalize" the price.

Related: New step for Bitcoin's wild ride is futures trading

Futures are contracts that let investors buy or sell something at a specific price in the future.

Offering futures contracts for bitcoin allows investors to speculate on the digital currency's price without actually owning any bitcoin. That's good news for mainstream investors who want to place their bets on bitcoin, but may be nervous about purchasing the actual currency.

Related: A warning about bitcoin's wild price swings

The option also gives investors an easy way to bet against bitcoin, which could snap its streak of nearly unfettered gains.

There's been a few sharp dips, but bitcoin's rise has been stunning. In 2011, it once traded at less than a dollar, according to CoinDesk.

--Jethro Mullen and Daniel Shane contributed to this report.